1. Field of the Invention
This invention relates to image processing, and in particular, it relates to a method for improving the quality of a scanned image of a document.
2. Description of Related Art
As information is increasingly being transmitted and consumed in digital forms, it is becoming an increasingly common practice to convert hard copies of documents into digital images using scanners. The scanning process, however, often introduces image distortions such as image shift and skew as well as random noises in the scanned image. Problems with such distortions and noises are present even for high-end scanners. Such distortions and noises adversely affect the appearance of the scanned image. Moreover, when the scanned image is subject to further digital processing such as document authentication, the distortions and noises introduced in the scanning process often impair such processing.
Document authentication refers to a process by which a printed document, which has been distributed and circulated in its hard copy form, and may have been photocopied, is examined to determine whether its content has been altered since it was first printed. Some authentication techniques can determine what the alterations are. Alteration may occur as a result of accidental events or deliberate effort. In one form of document authentication, information regarding the content of the document is associated with the document itself. For example, such information may be encoded in two-dimensional barcode printed on the document itself or on the backside of the document. When the hard copy of a document is scanned back, the barcode is read and the data encoded in the barcode is extracted. The scanned document is analyzed using the information extracted from the barcode to determine whether the document is authentic (i.e. whether alterations have been made, or what the alterations are). In another form of document authentication, information regarding the document is stored in digital form in a reference database, and scanned document is analyzed using the information stored in the database to determine its authenticity.